Patent Document 1 discloses an image sensor in which a back incident-type CCD (a charge-coupled device) is disposed at a previous stage in an incident direction of light to be measured, and at a subsequent stage of the CCD, a photodiode array made of InGaAs is disposed. In the image sensor of this document, the CCD and photodiode array are connected via bumps, and signals from respective channels of the photodiode array are read out by a shift register formed on the CCD.
Patent Document 2 discloses one in which a CCD made of Si is disposed at an upper stage with respect to an incident light and an image sensor made of InGaAs is disposed at a lower stage.
Patent Document 3 discloses an image sensor for which two HgCdTe photodiode arrays are disposed side by side to be increased in dimension in the length direction. This is because it is difficult to fabricate a HgCdTd photodiode that is long in length on its own. When two photodiode arrays are placed side by side horizontally, the pixel pitch is likely to change at the position of a boundary between these photodiode arrays. In order to prevent this, two photodiode arrays have been overlapped in part. When photodiode arrays are disposed side by side, a photodiode (PD) present at a position closest to an end portion of each photodiode array becomes deteriorated in characteristics. In Patent Document 3, photodiodes located in the end portions are removed.